1. Field of the Invention
The present invention relates to a video signal playback system such as a video tape recorder and a video disc player, and more particularly, to a drop out compensation circuit to compensate for portions of decreased amplitude in video signals from a video head.
2. Description of the Background Art
Generally, a drop out compensation circuit envelope-detects the frequency modulation reproduced output from a video head, detects a portion where the envelope detected output is lower than a predetermined level, and compensates the low level portion with the FM reproduced output in an immediately previous horizontal 1H period. 1H The video signal has line correlativity and the gap of one horizontal period appearing on a screen has no effect on the human vision.
Such method of detecting a decrease in the envelope level, however, responds to a level decrease of a long duration such as a level decrease during high speed playback and a level decrease during the first half or the latter half of a field due to poor contact between a tape and a head. Therefore, when the drop out compensation is performed by a drop out compensation circuit employing a 1H delay circuit, as image signals for 1H are used repeatedly during the level decrease period, the pictorial image becomes rather unnatural.